415 



In the laboratory, each benthic biology sample was transferred to 70 percent 

 alcohol, stained with Rose Bengal and examined under a dissecting microscope. All 

 organisms were sorted to basic taxonomic groups such as polychaete families, amphipods, 

 isopods, other Crustacea, molluscs, echinoderms, etc. Identifications then were made to 

 the lowest possible taxon, usually species. Verification of the identity of voucher 

 specimens and probleinatic species was performed by outside taxonomic experts. Wet- 

 weight biomass was determined separately for each species. 



All data from each sampling cruise were coded at Battelle and entered into 

 the VAX 11/780 computer at Woods Hole Oceanographic Institution. Statistical treatment 

 of the data set included an agglomerative clustering technique to determine similarity 

 between samples. The similarity measure was NESS, the Normalized Expected Species 

 Shared, where the comparison of expected species shared is between random samples of 

 50 or 200 individuals from the initial collection of individuals in each grab. NESS is more 

 sensitive to the less common species than the other commonly used methods. The 

 clustering strategy was flexible sorting with set at the commonly used value of -0.25. 

 We also have used the Bray-Cjrtis or percent similarity coefficient as a similarity 

 measure with group average sorting. In addition, the Shannon-Wiener diversity (H') was 

 calculated and Hurlberfs modification of the rarefaction method was used to predict the 

 number of species in a random sample without replacement. 



6. RESULTS FOR THE FIRST YEAR OF THE BENTHIC INFAUNA MONITORING PROGRAM 



6.1 Sediments 



Sediments at all regional stations except Station 13 consisted of greater than 

 95 percent sand. Sediments at Station 13 consisted of nearly equal parts very fine sand 

 and silt/clay. At Stations 16, 17, and 18 near the rig site in Block i*10, sediinents were 

 dominated by coarse to medium sands. However, Station 18 had a higher proportion of 

 fine sand than Stations 16 and 17. There was no change in the percent of very fine sand or 

 silt/clay between the first (predrilling) and fourth (postdriUing) cruises. The sediments at 

 the 19 primary site-specific stations were very similar. However, sediments at Station 5- 

 29, the station farthest west of the rig site, had a higher proportion of very fine sand and 

 silt/clay than did the other stations. The percentage of fine sand at many site-specific 

 stations was highest in February. 



